We study the random walk of multiple photons in a massively multichannel system. The network consists of 3300 nearest-neighbour coupled silicon nitride waveguides embedded in silica. The photon correlations arising from the quantum interference between multiple single photons is measured using an intensified CCD at the output of the network. We further aim to control the multiphoton correlations in the network by structuring the incident states of quantum light. This procedure enables a versatile platform for studying quantum correlations, such as multiphoton boson sampling, without modifying the physical system. We will report on the latest progress in this experiment.
We study the random walk of multiple photons in a massively multichannel system. The network consists of 3300 nearest-neighbour coupled silicon nitride waveguides embedded in silica. The photon correlations arising from the quantum interference between multiple single photons is measured using an intensified CCD at the output of the network. We further aim to control the multiphoton correlations in the network by structuring the incident states of quantum light. This procedure enables a versatile platform for studying quantum correlations, such as multiphoton boson sampling, without modifying the physical system. We will report on the latest progress in this experiment.
Summary form only given. Quantum optics experiments require ultimate control over the propagation of light in linear optical networks to realize programmable photon correlations [1]. Integrated optics provides a robust and low-loss platform for implementing such linear optical networks. However, to achieve ultimate control on the quantum state of light, it is necessary to program the network [2]. Tuning the network for controlled multiphoton correlations involves optimization algorithms which scale inefficiently with the network size and photon number. Therefore, it is challenging to scale up this approach to massively multichannel networks, which are required for large-scale implementations of quantum information processing and quantum communication.Here, we propose a novel method to achieve ultimate control on quantum light propagation through the adaptive control of phases at input channels of a massively multichannel network. We utilize an on-chip array of 3300 nearest-neighbor coupled silicon nitride waveguides as the network. We employ complex wavefront shaping methods, which enabled the creation of programmable linear optical networks in opaque scattering media [3,4], to realize a network with programmable quantum correlations in a fixed network [5]. Using a high brightness photon-pair source, we demonstrate programmable Hong-Ou-Mandel-like bunching or antibunching of photons in a fully tunable multichannel network as predicted by our theoretical work [6]. These results enable programmable photon correlations on fixed massively multichannel optical networks with the potential for large-scale implementation of quantum simulators and quantum logic gates. We will report on the progress of this project.
Interference of multiple photons via a linear-optical network has profound applications for quantum foundation, quantum metrology, and quantum computation. Particularly, a boson sampling experiment with a moderate number of photons becomes intractable even for the most powerful classical computers. Scaling up from small-scale experiments requires highly indistinguishable single photons, which may be prohibited for many physical systems. Here we report a time-resolved multiphoton interference experiment by using photons not overlapping in their frequency spectra from three atomic-ensemble quantum memories. Time-resolved measurement enables us to observe nonclassical multiphoton correlation landscapes, which agree well with theoretical calculations. Symmetries in the landscapes are identified to reflect symmetries of the optical network. Our experiment can be further extended to realize boson sampling with many photons and plenty of modes, which thus may provide a route towards quantum supremacy with nonidentical photons.
Multiphoton interference is crucial to many photonic quantum technologies. In particular, interference forms the basis of optical quantum information processing platforms and can lead to significant computational advantages. It is therefore interesting to study the interference arising from various states of light in large interferometric networks. Here, we implement a quantum walk in a highly stable, low-loss, multiport interferometer with up to 24 ultrafast time bins. This time-bin interferometer comprises a sequence of birefringent crystals which produce pulses separated by 4.3\,ps, all along a single optical axis. Ultrafast Kerr gating in an optical fiber is employed to time-demultiplex the output from the quantum walk. We measure one-, two-, and three-photon interference arising from various input state combinations, including a heralded single-photon state, a thermal state, and an attenuated coherent state at one or more input ports. Our results demonstrate that ultrafast time bins are a promising platform to observe large-scale multiphoton interference.
Multiphoton interference is crucial to many photonic quantum technologies. In particular, interference forms the basis of optical quantum information processing platforms and can lead to significant computational advantages. It is therefore interesting to study the interference arising from various states of light in large interferometric networks. Here, we implement a quantum walk in a highly stable, low-loss, multiport interferometer with up to 12 ultrafast time bins. This time-bin interferometer comprises a sequence of birefringent crystals that produce pulses separated by 4.3 ps, all along a single optical axis. Ultrafast Kerr gating in an optical fiber is employed to time-demultiplex the output from the quantum walk. We measure one-, two-, and three-photon output states arising from various input state combinations, including a heralded single-photon state, a thermal state, and an attenuated coherent state at one or more input ports. Our results demonstrate that ultrafast time bins are a promising platform to observe large-scale multiphoton interference.
Multiphoton quantum correlations are crucial for quantum information processing and quantum communication protocols in linear optical networks. For large-scale implementation of quantum information processing, such as quantum simulators, boson sampling or programmable quantum logic gates, a programmable functionality of a large multichannel network is required. In this thesis, we describe and demonstrate programmable quantum interference between multiple single-photon states in massively multichannel networks. Using a theoretical analysis we first show that losses in optical networks, which are unavoidable in experiments, introduce new freedom, in that the functionality of the network, and thus also quantum interference in there, is programmable to an extent not possible with lossless networks. We introduce a method to program the functionality of general multichannel linear optical networks by phase modulation of incident wavefronts, which we apply to opaque scattering media as well as integrated optics. To demonstrate quantum interference in massively multichannel networks we require a source of multiple indistinguishable single-photon states. Therefore, we have constructed and characterized a versatile quantum light source based on spontaneous parametric down-conversion. For the first time, we demonstrate two-photon quantum interference in a massively multichannel linear optical network realized in an opaque scattering medium. Using adaptive phase-modulation of the incident photons, the scattering medium is transformed to behave as a fully programmable beam splitter that is freely tunable in functionality. Exploiting this freedom, we not only show the well-known Hong-Ou-Mandel bunching of photons, but also demonstrate that this bunching can be made to vanish, or be transformed into antibunching. Our results establish opaque scattering media as a platform for massively multichannel linear optical networks with programmable quantum correlations. Finally, the high number of available channels offered by opaque scattering media can directly be employed for authentication of secure communication. We present an authenticated protocol for quantum key distribution that removes the need of an initial shared secret for authentication. Moreover, we introduce and demonstrate the first protocol for authenticated and asymmetric quantum communication, based on the quantum-secure readout of a physical unclonable function.
Quantum interference and quantum correlation, as two main features of quantum optics, play an essential role in quantum information applications, such as multi-particle quantum walk and boson sampling. While many experimental demonstrations have been done in one-dimensional waveguide arrays, it remains unexplored in higher dimensions due to tight requirement of manipulating and detecting photons in large-scale. Here, we experimentally observe non-classical correlation of two identical photons in a fully coupled two-dimensional structure, i.e. photonic lattice manufactured by three-dimensional femtosecond laser writing. Photon interference consists of 36 Hong-Ou-Mandel interference and 9 bunching. The overlap between measured and simulated distribution is up to 0.890 ± 0.001. Clear photon correlation is observed in the two-dimensional photonic lattice. Combining with controllably engineered disorder, our results open new perspectives towards large-scale implementation of quantum simulation on integrated photonic chips.